1. Field of the Invention
The present invention relates generally to a surgical robot, and more particularly, to a handheld robot for orthopedic surgery and the control method thereof. The handheld robot of the present invention is able to combine the position/orientation information of a tool acquired by a positioning unit with the force/torque information acquired by a force sensor, and is able to utilize the combined information to compensate the motion of the handheld robot.
2. The Prior Arts
In the field of orthopedic surgery, surgical jigs, computer aided navigation program or image-guided robotic arm are commonly used to assist surgeons to position the bones during the operation, such as an osteotomy, or surgeries that requires the surgeon to place plant bone plates or bone screws into patients.
In a surgery where surgical jigs are used to help with the measuring and the positioning of the cut, surgeons often need to switch surgical jigs during one operation multiple times, which can lead to errors in the positioning. In addition, the use of a surgical jig also depends on factors such as the familiarity of the surgeon with the surgical jig, the level of operation technique of the surgeon and clinical experience of the surgeon. In orthopedic surgeries where computer aided navigation program is used for positioning, the navigation program guides the surgeon to position/orientate the cutting block, so as to mount the cutting block on the bones of the patient. However, in the actual surgeries, surgeons need to constantly adjust the cutting block manually to position/orientate the cutting block as instructed by the navigation program, which complicates the positioning process. In recent years, some solutions have been developed addressing the abovementioned issue. For example, an adjusting screw can be used to finely adjust the position/orientation of the cutting block. However, in the process of mounting the cutting block with the adjusting screw, the precision of the result might still be compromised due to the error occurred during the process of fixing the adjusting screw.
In orthopedic surgeries with image-guided robotic arms, medical images and robotics are used for the positioning. Before the surgery is performed, surgeons would acquire computer tomography (CT) image first so as to prepare the surgery by planning the operation path. During the surgery, first, the bone of the patient is immobilized, and a position system is used to monitor if the bone is moving. If the bone of the patient moved during the operation, the positioning system immediately starts the re-coordination procedure to ensure the precision and the safety of the operation. Alternatively, surgeons can utilize the positioning system to measure the relative position and orientation between the bone and the robotic arm, and further perform precise positioning and bone cutting through dynamic motion compensation control. Herein, the optical positioning system is one of the most commonly used positioning systems in the medical industry. The optical positioning system utilize an optical tracker to tack the light-reflecting balls disposed on the bones and the robotic arm, thereby determining information such as the relative position, relative orientation and relative speed between the robotic arm and the patient. Subsequently, the image-guided robotic arm use the above information along with a control method to determine if the parameters of the patient and the equipment are compliant with the surgical procedure, and further compensate the position and orientation of the tool with regard to the patient. However, due to the response bandwidth of the optical positioning system, the reaction speed of the robotic arm is limited, which compromises the precision of the operation. In addition, blockage is a more serious matter which occurs quite often in the optical positioning system. When the light-reflecting balls are blocked by obstacles, the optical positioning system cannot provide the relative position and orientation between the bones and the robotic arm. Hence, in the situation where only optical positioning system is used to assist with the motion compensation of the robotic arm, the position of the robotic arm cannot be adjusted in time, which can endanger the safety of the patient. Furthermore, compared with the conventional bone cutting tool, the size of the robotic arm is way too huge, which causes inconveniences for the surgeons, and also limits the application thereof.
On the other hand, in the conventional control methods for robotic arms that utilizes medical images and positioning information to compensate the motion thereof, in order to prevent the tool from damaging the blood vessels, nerves or soft tissues of the patient, current control methods simply turn off the motor when the front end of the tool deviates from the predetermined operation range/path. Such control methods lack the ability to keep the front end of the tool within the range/path of the operation plan; therefore, surgeons need to control the movement of the robotic arm manually through out the whole operation process, which can be very exhausting.